The field of the invention relates to an image processing system in general, and in particular to an apparatus for providing optical differentiation between two images to be used as inputs for a Kalman filter algorithm.
An extended Kalman filter algorithm is a computerized technique developed in the general area of estimation theory for nonlinear systems. The algorithm is a sophisticated technique of performing an error analysis on real time measurements and making corresponding corrections to a system state. Typically, the Kalman filter algorithm is used with space navigation systems and usually involves the use of a covariance matrix and weighting coefficients. For more information about Kalman filter algorithms, see The Kalman Filter: Its Recognition and Development for Aerospace Applications American Institute of Aeronautics and Astronautics, Inc., Journal of Guidance and Control, Jan.-Feb. 1981, pg. 4. Also see Least-squares estimation: from Gauss to Kalman, IEEE Spectrum, Jul. 1970, pg 63. Another good reference is An Adaptive Extended Kalman Filter for Target Image Tracking, IEEE Transactions on Aerospace and Electronic Systems, Vol. AES-17, No. 2, Mar. 1981, pg 173.
At the present time, computer usage of the extended Kalman filter algorithm requires the calculation of three preliminary functions in order to be able to utilize the algorithm with data that is collected optically. Presently, these three functions are calculated digitally by the same computer used to execute the extended Kalman filter algorithm. Unfortunately, the computation of these functions by digital computers at video rates requires prohibitively high data rates for images larger than 8.times.8 pixels. Consequently, the digital computer is unable to efficiently perform lower data rate tasks required by the Kalman filter algorithm such as matrix manipulations and multiplications.
U.S. Pat. No. 3 888,591 discloses a system for subtracting two images utilizing encoding and filtering means. U.S. Pat. No. 4,075,604 teaches an apparatus having sampling means for real time recognition of test images by comparison with sample images. While both patents are useful devices for their intended purposes, they are unsuitable for providing the three parameters needed in executing an extended Kalman filter algorithm.